A conventional device for controlling an amount of hot dip galvanization adhesion controls the amount of hot dip galvanization adhesion by spraying gas from a wiping nozzle onto a steel plate to which molten metal adheres. Such a device is devised such that a pressure control valve and an opening control valve are arranged in series to increase a response speed of a spraying amount of this gas.
FIG. 11 is a schematic view explaining the conventional device for controlling the amount of hot dip galvanization adhesion. As illustrated in FIG. 11, the conventional device for controlling the amount of hot dip galvanization adhesion includes a first valve opening degree setter 113a, a second valve opening degree setter 113b, a gas supply device 115, a receiver tank 116, a first pressure control valve 117a, a second pressure control valve 117b, an opening control valve 118, a first a pressure gauge 119a, a first b pressure gauge 119b, a second pressure gauge 120, a third pressure gauge 121, a first wiping nozzle 122, and a second wiping nozzle 123. Note that the solid-line arrows in the FIG. 11 indicate a duct through which the gas flows.
The first wiping nozzle 122 and the second wiping nozzle 123 communicate with the gas supply device 115 via the duct and spray the gas supplied from the gas supply device 115 respectively onto front and back sides of the steel plate to which the molten metal adheres.
The receiver tank 116 is installed in the duct downstream of the gas supply device 115, and has a diameter greater than that of the duct. Moreover, the third pressure gauge 121 measures a gas pressure (that is a pressure of the gas supplied from the gas supply device 115) P3′ inside the receiver tank 116.
The opening control valve 118 is installed in the duct downstream of the gas supply device 115 and the receiver tank 116 and controls the opening degree of the duct. The second pressure gauge 120 is installed downstream of the opening control valve 118 and measures a gas pressure P2′ in the duct.
Note that the duct branches in two directions downstream of the second pressure gauge 120, and branched portions of the duct communicate respectively with the first wiping nozzle 122 and the second wiping nozzle 123.
The first pressure control valve 117a and the second pressure control valve 117b are pressure control valves installed respectively in the branched portions of the duct, upstream of the first wiping nozzle 122 and the second wiping nozzle 123. A positional relationship between the opening control valve 118 and the first pressure control valve 117a and a positional relationship between the opening control valve 118 and the second pressure control valve 117b are referred to as arranged in series.
The first a pressure gauge 119a measures a gas pressure in the duct between the first pressure control valve 117a and the first wiping nozzle 122, that is a gas pressure P1a′ of the first wiping nozzle 122. The first b pressure gauge 119b measures a gas pressure in the duct between the second pressure control valve 117b and the second wiping nozzle 123, that is a gas pressure P1b′ of the second wiping nozzle 123.
The first valve opening degree setter 113a performs feedback control (one-dot chain line arrows in FIG. 11) of the first pressure control valve 117a, based on a measurement result of the first a pressure gauge 119a, such that the gas pressure P1a′ becomes equal to a set gas pressure P1a. Meanwhile, the second valve opening degree setter 113b performs feedback control (one-dot chain line arrows in FIG. 11) of the second pressure control valve 117b, based on a measurement result of the first b pressure gauge 119b, such that the gas pressure P1b′ becomes equal to a set gas pressure P1b. Note that P1a=P1b is normally satisfied in most cases.